Build identifier: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:7.0a2) Gecko/20110720 Firefox/7.0a2
Steps to reproduce:
1. Open Aurora with a clean profile
2. Go to Bookmarks -> Show all Bookmarks
3. In the Bookmarks Toolbar list of bookmarks try to drag one of the folders up or down to reorganize
4. Crash!
Expected result would be to re-order the list.

Created attachment 547742[details][diff][review]
null check data
This bug is caused because bookmarks appears to be setting text/plain drag data to some non-string. This patch fixes the crash on Mac at least.
Marco, the bookmarks code is still doing something wrong here. Can you debug where this might be happening?

Created attachment 552184[details][diff][review]
patch, version 2
The cause of the failure is related to bug 564688. On Windows and Linux, when the text/unicode data is not valid an error is returned when the data is retrieved, which means that the flavour is added but the data is just empty. On Mac, the data for strings is determined when the data is placed on the clipboard rather than when it is retrieved, so we need to put something there to indicate that the flavour is present.
This version of the patch adds an empty string instead when the data cannot be converted.
Ideally, we would change the clipboard handling to validate the data when it is placed on the clipboard.

Comment on attachment 552184[details][diff][review]
patch, version 2
I think we should backport this fix since users on osx are crashing easily just by dragging bookmarks, and the fix is small and safe enough

(In reply to AndreiD[QA] from comment #18)
> There is no crash if following the steps in the description, on the current
> (up to date) Aurora and Firefox 7b5:
> Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:7.0) Gecko/20100101
> Firefox/7.0
> Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0a2) Gecko/20110908
> Firefox/8.0a2
> Setting this bug as Verified Fixed.
Also there is no crash if following the steps in the description on the latest Firefox Nightly build:
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:9.0a1) Gecko/20110911 Firefox/9.0a1
So the issue is verified fixed at all Firefox development stages: nightly, aurora and beta.